Method of delivering a stent

ABSTRACT

A guidewire loaded stent for delivery through a catheter is described herein. The stent delivery assembly can deliver and place a stent within tortuous regions of the body which are accessible to guidewires but inaccessible to stenting catheters. The assembly comprises a guidewire covered in part by a retractable sheath and a radially expandable stent near or at the distal end of the guidewire. The whole assembly is advanced through conventional catheters or it may be used alone. In either case, when the stent is adjacent to a treatment site within the body, the sheath is retracted proximally to expose the stent for radial expansion into contact with the vessel wall. Radio-opaque marker bands are optionally located on either side or both sides of the stent on the guidewire body to aid in visual placement. The assembly can optionally include an expandable balloon on the guidewire for different treatment modalities.

This application is a continuation of application Ser. No. 11/248,362,filed Oct. 11, 2005 which is a continuation of application Ser. No.10/087,127, filed Feb. 28, 2002, now U.S. Pat. No. 6,989,024, the entirecontents of which are incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to catheters and intravascularmedical procedures. More particularly, it relates to methods andapparatus for delivering a stent through a catheter by way of aguidewire delivery device.

BACKGROUND ART OF THE INVENTION

Intravascular stents are well known in the medical arts for thetreatment of vascular stenoses. Stents are prostheses which aregenerally tubular and which expand radially in a vessel or lumen tomaintain its patency. For deployment within the body's vascular system,most stents are mounted onto a balloon angioplasty catheter fordeployment by balloon expansion at the site of a dilated stenosis or ananeurysm. Self-expanding stents, which typically expand from acompressed delivery position to its original diameter when released fromthe delivery device, generally exert a radial force on the constrictedportion of the body lumen to re-establish patency. One commonself-expanding stent is manufactured of Nitinol, a nickel-titanium shapememory alloy, which can be formed and annealed, deformed at a lowtemperature, and recalled to its original shape with heating, such aswhen deployed at body temperature in the body.

To position a stent across an area of stenosis or an aneurysm, a guidingcatheter having a preformed distal tip is percutaneously introduced intothe vascular system of a patient by way of, e.g., a conventionalSeldinger technique, and advanced within the vasculature until thedistal tip of the guiding catheter is seated in the ostium of a desiredartery. A guidewire is then positioned within an inner lumen of adilatation catheter and then both are advanced through the guidingcatheter to the distal end thereof. The guidewire must first be advancedout of the distal end of the guiding catheter into the patient'scoronary vasculature until the distal end of the guidewire crosses alesion to be dilated, then the catheter having a stent positioned on thedistal portion is advanced into the patient's vasculature over thepreviously introduced guidewire until the stent is properly positionedacross the lesion. Once in position, the stent may be releasedaccordingly.

It is generally desirable to have catheters which present small crosssectional diameters to enable access into small sized vessels. However,conventional techniques and apparatus typically require the use of aguidewire for the desirable placement of the catheter and stent withinthe vasculature. Thus, conventional catheters typically require aseparate lumen within the catheter body to allow for the passage of aguidewire therethrough. This separate lumen necessarily adds to thecross sectional profile of the device. Yet vasculature having a tortuouspath and/or a small diameter, such as the intracranial vasculature,present problems for the conventional stenting catheter. Accordingly, ahighly flexible stenting apparatus which is capable of accessingtortuous regions and which presents a small cross section is needed.

SUMMARY OF THE INVENTION

A highly flexible stent delivery assembly is described below. Theassembly has the desirable characteristics of guidewires in traversingtortuous vasculature, including small cross sectioned vessels. The stentdelivery assembly of the present invention is thus able to deliver andplace a stent anywhere in the vasculature or within the body that isreadily accessible by a guidewire but is not normally accessible by astenting catheter body which would ride over such a guidewire.

The stent delivery assembly may typically comprise a guidewire bodywhich is preferably covered at least in part by a retractable sheath. Aradially expandable stent is disposed directly in contact about theguidewire preferably near or at the distal end of the guidewire. Theretractable sheath preferably covers the entire stent during deploymentand placement, and is retractable proximally to uncover or expose thestent for radial expansion. A pair of optionally placed radio-opaquemarker bands may be located on either side (distally or proximally) orboth sides of the stent on the guidewire body.

The sheath may have a flush port, which is in fluid communication withthe distal end of the assembly, located near the proximal end of thesheath. The flush port enables a fluid, e.g., saline, to be passedthrough the assembly prior to insertion into the vasculature forflushing out air or debris trapped between the sheath and guidewire. Itmay also be used to deliver drugs or fluids within the vasculature asdesired.

Because the guidewire body, rather than a catheter body, carries anddelivers the stent through the vasculature, the stent may be placedalmost anywhere in the body accessible by a conventional guidewire. Thismay include, e.g., the tortuous intracranial vasculature as well as,e.g., the more accessible coronary vasculature. Furthermore, theassembly, which may include the guidewire, sheath, and stent, may beintroduced into a wide variety of conventional catheters. Thisportability allows for flexibility in using the same type of assembly inan array of conventional catheters depending upon the desiredapplication and the region of the body to be accessed.

The sheath may be made from various thermoplastics, e.g., PTFE, FEP,Tecoflex, etc., which may optionally be lined on the inner surface ofthe sheath or on the outer surface of the guidewire or on both with ahydrophilic material such as Tecoflex or some other plastic coating.Additionally, either surface may be coated with various combinations ofdifferent materials, depending upon the desired results. It is alsopreferably made to have a wall thickness of about, e.g., 0.001 in.,thick and may have an outer diameter ranging from about 0.0145 to 0.016in. or greater. The sheath may be simply placed over the guidewire andstent, or it may be heatshrinked to conform closely to the assembly.

The guidewire body may be made of a conventional guidewire or it mayalso be formed from a hypotube having an initial diameter ranging from0.007 to 0.014 in. Possible materials may include superelastic metalsand alloys, e.g., Nitinol, or metals such as stainless steel, ornon-metallic materials, e.g., polyimide. The hypotube may be furthermelted or ground down, depending upon the type of material used, intoseveral sections of differing diameters. The distal end of the guidewiremay be further tapered and is preferably rounded to aid in advancementthrough the vasculature. Radio-opaque coils may be placed over a portionof distal end to aid in radiographic visualization.

The stent may be configured to be self expanding from a constrainedfirst configuration when placed upon guidewire to a larger expandedsecond configuration when deployed. When the sheath is retractedproximally, the stent preferably self expands to a preconfigureddiameter of, e.g., about 0.060 in. (1.5 mm), and up to a diameter ofabout 0.315 in. (8 mm). Various materials may be used to construct thestent such as platinum, Nitinol, other shape memory alloys, or otherself expanding materials.

Other variations may include a guidewire which defines a stepped sectionnear the distal end of the guidewire. The stepped section outer diameteris less than the uniform diameter defined by the remainder of theguidewire. The stent may be placed over this section while maintaining aflush outer diameter which may facilitate delivery of thestent-guidewire assembly not only through catheter body but within thevasculature. The guidewire may be further formed into tapered sectiondistally of the stepped section.

When in use in tortuous pathways, such as intracranial vessels, theguidewire assembly may be used with the sheath alone or in combinationwith a delivery catheter. The catheter body may be advanced within thevessel to a treatment location such as an aneurysm. Once the catheter isnear the treatment site, the guidewire may be advanced out of thecatheter and adjacent the treatment site. The sheath may then beretracted proximally to expose the stent to radially expand into contactwith the walls of the vessel. Alternatively, the sheath may be heldstationary while the guidewire and stent are advanced to expose thestent, e.g., as when deploying a coil stent. The stent may be selfexpanding or configured to expand upon the application of an electriccurrent with or without the sheath. In either case, once the stent hasbeen released from the guidewire and expanded, both the guidewire andsheath may be withdrawn into the catheter body and removed from thevicinity. The catheter may be left within the vessel to allow for theinsertion of additional tools or the application of drugs near thetreatment site.

Other variations may include an expandable balloon section preferablylocated distally of the stent. In this case, treatment preferablyincludes the expansion of the balloon first to mitigate any occlusionswithin the vessel. The stent may then be released in a manner similar tothat described above. Once the balloon has been deflated and the stentexpanded, the assembly may be removed from the vicinity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a variation on the stent delivery assembly where aguidewire has a stent disposed on the wire near its distal end.

FIG. 1B shows another variation on the assembly where the guidewire mayhave an expandable balloon located near the distal end of the wire.

FIG. 2 shows a representative illustration of the guidewire and stentassembly which is insertable within a catheter; the assembly shows theguidewire surrounded by a partially retracted sheath which exposes thestent.

FIG. 3 shows a cross sectioned side view of a variation of the stentdelivery assembly placed within a catheter body lumen.

FIG. 4 shows a cross sectioned side view of another variation of thestent delivery assembly also placed within a catheter body lumen.

FIG. 5 shows a cross sectioned side view of yet another variation of thestent delivery assembly having an expandable balloon section.

FIGS. 6A to 6C illustrate an example of one method of placing a stentwithin a hollow body organ using the guidewire assembly.

FIGS. 7A to 7C illustrate an example of another method of placing astent within the hollow body organ in combination with an expandableballoon.

DETAILED DESCRIPTION OF THE INVENTION

A stent delivery assembly having a small cross section and which ishighly flexible is described herein. As shown in FIG. 1A, catheterassembly 10 is comprised of a conventional catheter body 12 having adistal end 14 and a proximal end 16. A fitting assembly 18 is attachedto the proximal end 16 and may preferably have various attachments,e.g., Luer lock 20, to allow for access to catheter body 12 or the useof other instruments. Conventional catheter body 12 shows guidewireassembly 22 being slidably positioned therewithin. Assembly 22, which isdescribed in further detail below, is shown in this variation as havinga guidewire body 24 preferably covered at least in part by a retractablesheath 26. A radially expandable stent 28 is preferably disposed nearthe distal end of guidewire 24. Stent 28 may also be placed between anoptional pair of radio-opaque marker bands 30, 32. One or both markerbands 30, 32 may be used or they may be left off the assembly entirely.The use of radio-opaque material allows for the visualization of theassembly during placement within the vasculature. Such visualizationtechniques may include conventional methods such as fluoroscopy,radiography, ultrasonography, magnetic resonance imaging, etc.

FIG. 1B shows the distal portion of catheter body 12 with anotherguidewire variation 34 which has an optional angioplasty balloon 36. Asshown in this variation, balloon 36 is preferably located distally ofstent 28 and may be sufficiently deflated such that sheath 26 may beplaced over both stent 28 and balloon 36.

FIG. 2 shows a representative illustration of the stent deliveryassembly 40 removed entirely from the delivery catheter body withguidewire 24 covered by sheath 26. Stent 28 is preferably placeddirectly over guidewire body 24 and is covered by sheath 26. Sheath 26may have a flush port 42 located near the proximal end of the sheath 26.Flush port 42 is preferably in fluid communication with the distal endof the assembly 40 so that a fluid, e.g., saline, may be passed throughthe assembly 40 prior to insertion into the vasculature for flushing outair or debris trapped between the sheath 26 and guidewire 24. Flush port42 may also be used to deliver drugs or fluids within the vasculature asdesired.

Because the guidewire body 24, rather than a catheter body, carries anddelivers stent 28 through the vasculature, the stent 28 may be placedalmost anywhere in the body accessible by a conventional guidewire. Thismay include, e.g., the tortuous intracranial vasculature as well as,e.g., the more accessible coronary vasculature. Furthermore, assembly40, which may include the guidewire 24, sheath 26, and stent 28, may beintroduced into a wide variety of conventional catheters. Thisportability of assembly 40 allows for flexibility in using the same typeof assembly 40 in an array of conventional catheters depending upon thedesired application and the region of the body to be accessed.

The sheath 26 may be made from various thermoplastics, e.g., PTFE, FEP,Tecoflex, etc., which may optionally be lined on the inner surface ofthe sheath or on the outer surface of the guidewire or on both with ahydrophilic material such as Tecoflex or some other plastic coating.Additionally, either surface may be coated with various combinations ofdifferent materials, depending upon the desired results. Sheath 26 ispreferably made to have a wall thickness of about 0.001 in. thick, andoptionally thicker, and may have an outer diameter ranging from about0.0145 to 0.016 in., or greater. Sheath 26 may also be placed overguidewire body 24 having a diameter of about 0.038 in. When placed overguidewire body 24 and stent 28, it may be simply placed over to slidealong wire 24 or it may also be heatshrinked over the wire 24 and stent28 to conform closely to the assembly.

A more detailed view of the guidewire assembly is shown in the crosssectioned side view in FIG. 3. As seen, the distal end of guidewire body24 is shown loaded within sheath lumen 60 of sheath 26 and this assemblyis shown as being disposed within catheter lumen 62 of catheter body 12.As previously discussed, because stent 28 is placed upon a guidewirebody rather than a catheter body, the assembly may be introduced intoany part of the body which is accessible by a conventional guidewire butwhich is not normally accessible for stenting treatments.

The guidewire body 24 may be made of a conventional guidewire and it mayalso be formed from a hypotube having an initial diameter ranging from0.007 to 0.014 in. The hypotube or guidewire may be made from a varietyof materials such as superelastic metals, e.g., Nitinol, or it may bemade from metals such as stainless steel. During manufacture, a proximaluniform section 50 of the hypotube may be made to have a length ofbetween about 39 to 87 in. (100 to 220 cm), preferably between about 63to 71 in. (160 to 180 cm), having the initial diameter of 0.007 to 0.022in., preferably 0.008 in. The hypotube may be further melted or grounddown into a tapered section 52, depending upon the type of materialused, which is distal to the proximal uniform section 50. Taperedsection 52 may have a length of about 4 in. (10 cm) to reduce thediameter down to about 0.002 to 0.003 in. The hypotube may be furtherformed to have a distal uniform section 54 of about 2 in. (5 cm) inlength over which the stent 28 is preferably placed. Radio-opaque markerbands may optionally be placed either distally 30 or proximally 32 ofstent 28 to visually aid in the placement of the stent 28, as is wellknown in the art. Alternatively, distal and proximal marker bands 30, 32may be eliminated altogether. Marker bands 30, 32 may be used as blocksor stops for maintaining the stent in its position along guidewire body24. Alternatively, if bands 30, 32 are omitted from the device, stops orblocks may be formed integrally into the guidewire body 24 or they maybe separately formed from material similar to that of guidewire body 24and attached thereto.

Distal end 56 may be further tapered beyond distal uniform section 54 toend in distal tip 58, which is preferably rounded to aid in guidewire 24advancement. A coil, preferably made from a radio-opaque material suchas platinum, may be placed over a portion of distal end 56.Alternatively, a radio-opaque material, e.g., doped plastics such asbismuth or tungsten, may be melted down or placed over a portion ofdistal end 56 to aid in visualization. Stent 28 is preferably made to beself expanding from a constrained first configuration, as when placedupon guidewire 24 for delivery, to a larger expanded secondconfiguration as when deployed within the vasculature. Stent 28 may beconstrained by sheath 26 to a diameter of, e.g., 0.014 in., while beingdelivered to a treatment site within the body, but when sheath 26 isretracted proximally, stent 28 preferably self expands to apreconfigured diameter of, e.g., about 0.060 in. (1.5 mm), and up to adiameter of about 0.315 in. (8 mm). Various materials may be used toconstruct stent 28 such as platinum, Nitinol, other shape memory alloys,or other self expanding materials. Sheath 26 may also have drainageports or purge holes 64 formed into the wall near the area coveringstent 28. There may be a single hole or multiple holes, e.g., threeholes, formed into sheath 26. Purge holes 64 allow for fluids, e.g.,saline, to readily escape from inbetween sheath 26 and guidewire 24 whenpurging the instrument, e.g., to remove trapped air or debris.

FIG. 4 shows a cross sectioned side view of another variation 70 of thestent delivery assembly. As shown, guidewire variation 70 is shown asbeing surrounded by sheath 26 and the sheath-guidewire assembly is shownas being placed within catheter lumen 62 prior to delivery of the stent.In this variation, the guidewire may have a uniform section 72 like thatdescribed in FIG. 3 above. However, there is also a stepped section 74defined in the guidewire outer diameter near the distal end of theguidewire. Within this section 74, the stepped outer diameter is lessthan the uniform diameter defined by the guidewire uniform section 72.It is over this stepped section 74 that stent 84 may be placed alongwith optional distal and/or proximal marker bands 80, 82, respectively,such that sheath 26 remains flush over this section. Maintaining a flushouter diameter may facilitate delivery of the stent-guidewire assemblynot only through catheter body 12 but within the vasculature. Theguidewire may be farther formed into tapered section 76 distally ofstepped section 74. And the guidewire may be finally formed into adistal tip 78 over which coil 86 may be optionally placed. Coil 86 mayoptionally be covered by a covering 88, e.g., a polymer or other plasticmaterial, placed or heatshrinked over the coil 86 and distal tip 78 toprovide a smooth section.

FIG. 5 shows a cross sectioned side view of yet another variation of thestent delivery assembly having an expandable balloon section. As shown,much of the guidewire is similar to variations described above but withthe addition of an expandable balloon 36 which may be inflated to anexpanded balloon 36′. The variation shown may have a uniform section 90which similarly tapers down 92 into a distal uniform section 94, overwhich stent 28 may be placed. Although balloon 36 may be placedproximally of stent 94, it is preferably located distally of stent 94,as shown. When deflated, retractable sheath 26 may also be placed overballoon 36 to provide a uniform profile. To accommodate the inflationand deflation of balloon 36, a small inflation lumen (not shown) may bedefined within the body of the guidewire for the passage of fluids intoand out of the balloon 36. A coil may also be optionally placed overdistal end 96; alternatively, a radio-opaque material may be melted downor placed over distal end 96.

In operation, the stent delivery guidewire may be used with or withoutthe catheter body to deliver the assembly intravascularly. It ispreferable that a catheter be used to provide a pathway close to thetreatment site. However, in tortuous pathways, such as intracranialvessels, the guidewire device may be used with the sheath alone if thecatheter body presents too large a cross section for delivery purposes.FIGS. 6A to 6C show an example of the deployment of the guidewireassembly. Catheter body 12 may first be advanced within the lumen 102 ofvessel 100 to a treatment location, e.g., aneurysm 104. Once catheterbody 12 has reached a position near aneurysm 104, guidewire 24 may beadvanced through and out of catheter 12 with sheath 26 covering stent28, as seen in FIG. 6A. As guidewire 24 is advanced, stent 28 located onguidewire 24 may be positioned via radio-opaque marker bands 30, 32 tothe desired location, such as over the neck 106 of aneurysm 104. Onceguidewire 24 and stent 28 have been properly positioned, sheath 26 maybe retracted proximally to expose stent 28 to the vascular environment,as shown in FIG. 6B.

Stent 28, as shown in FIG. 6C, may be left to radially self expand intogentle contact with the walls of vessel 100 to occlude the neck 106 ofaneurysm 104 (as is well known in the art). Stent 28 may also beconfigured to expand upon the application of an electric currentactuated from a location external of the patient. The current may bedelivered to stent 28 via an electrical connection or line (not shown)disposed within the body of guidewire 24. Once the stent 28 has beenreleased from the guidewire body 24 and expanded into contact withvessel 100, guidewire 24 and sheath 26 may be withdrawn into catheterbody 12 and removed entirely from catheter 12 or the catheter 12 itselfmay then be removed entirely from the body of the patient. If guidewire24 and sheath 26 are removed only, catheter 12 may be left in positionwithin vessel 100 to allow for the insertion of additional tools or theapplication of drugs near the treatment site.

Treatment may also be accomplished with the guidewire variation havingan expandable balloon section. FIG. 7A shows vessel 110 which isstenosed with an obstruction 112. Once catheter body 12 has beenpositioned within vessel 110, guidewire body 34 may be advanced out ofcatheter 12 while still covered by sheath 26. Balloon 36 may then bepositioned adjacent to the obstruction 112 optionally guided by markerbands 30, 32. Once positioned, balloon 36 may be expanded to balloon36′, as shown in FIG. 7B, to open the stenosed vessel. After theobstruction 112 has been opened, balloon 36 may be deflated and theguidewire body 34 may be advanced distally to position sheath 28adjacent to obstruction 112. Sheath 26 may then be retracted to exposestent 28 to expand, as described above, into contact against obstruction112 and vessel 110. FIG. 7C shows the placement of guidewire 34 andexpanding stent 28 over obstruction 112.

The applications of the guidewire assembly and methods of use discussedabove are not limited to the deployment and use within the vascularsystem but may include any number of further treatment applications.Other treatment sites may include areas or regions of the body such asorgan bodies. Modification of the above-described assemblies and methodsfor carrying out the invention, and variations of aspects of theinvention that are obvious to those of skill in the art are intended tobe within the scope of the claims.

What is claimed is:
 1. A method for treating an aneurysm located withinan intracranial vessel of a patient comprising: providing a radiallyself-expanding tubular prosthesis having a body defined by a cylindricalwall, the cylindrical wall having no circumferential free ends, at leasta portion of the cylindrical wall having a plurality of throughpassages, the radially self-expanding tubular prosthesis having anunexpanded and expanded configuration, said unexpanded configurationhaving first inner and outer diameters and said expanded configurationhaving second inner and outer diameters greater than the first inner andouter diameters, respectively; providing an elongated metallic wire,said elongated metallic wire being devoid of an internal through lumenthat extends between the proximal and distal ends and having a stop in afixed position, said stop having a diameter greater than the unexpandedfirst inner diameter of the proximal end of the radially self-expandingtubular prosthesis, the radially self-expanding tubular prosthesiscoaxially positioned in its unexpanded configuration on a distal segmentof the elongated metallic wire and distal to said stop and further beingfully releasable from the elongated metallic wire for placement across aneck of the aneurysm; providing an elongated sheath, said elongatedsheath being slidable between a first position covering and radiallyconstraining the radially self-expanding tubular prosthesis and a secondposition in which all of the radially self-expanding tubular prosthesisis uncovered, the radially self-expanding tubular prosthesis radiallyconstrained on the distal segment of the elongated metallic wire;delivering the radially self-expanding tubular prosthesis and theelongated sheath to the aneurysm, the radially self-expanding tubularprosthesis carried by the elongated metallic wire so that the portion ofthe cylindrical wall having the plurality of through passages ispositioned across the neck of the aneurysm; and sliding the elongatedsheath from the first position to the second position to fully releasethe radially self-expanding tubular prosthesis from the elongatedmetallic wire so that the radially self-expanding tubular prosthesis isplaced across the neck of the aneurysm in the expanded configuration,the elongated sheath at least partially constraining the radiallyself-expanding tubular prosthesis on the distal segment of the elongatedmetallic wire until the elongated sheath attains the second position. 2.A method for treating an aneurysm located within an intracranial vesselof a patient comprising: providing a radially self-expanding tubularprosthesis having a body defined by a cylindrical wall, the cylindricalwall having no circumferential free ends, at least a portion of thecylindrical wall having a plurality of through passages, the radiallyself-expanding tubular prosthesis having an unexpanded and expandedconfiguration, said unexpanded configuration having first inner andouter diameters and said expanded configuration having second inner andouter diameters greater than the first inner and outer diameters,respectively; providing an elongated metallic wire, said elongatedmetallic wire being devoid of an internal through lumen that extendsbetween the proximal and distal ends and having a block in a fixedposition, said block having a diameter greater than the unexpanded firstinner diameter of the proximal end of the radially self-expandingtubular prosthesis, the radially self-expanding tubular prosthesiscoaxially positioned in its unexpanded configuration on a distal segmentof the elongated metallic wire and distal to said block and furtherbeing fully releasable from the elongated metallic wire for placementacross a neck of the aneurysm; providing an elongated sheath, saidelongated sheath being slidable between a first position covering andradially constraining the radially self-expanding tubular prosthesis anda second position in which all of the radially self-expanding tubularprosthesis is uncovered, the radially self-expanding tubular prosthesisradially constrained on the distal segment of the elongated metallicwire; delivering the elongated sheath and the radially self-expandingtubular prosthesis to the aneurysm, the radially self-expanding tubularprosthesis carried by the elongated metallic wire so that the portion ofthe cylindrical wall having the plurality of through passages ispositioned across the neck of the aneurysm; and sliding the elongatedsheath from the first position to the second position to fully releasethe radially self-expanding tubular prosthesis from the elongatedmetallic wire so that the radially self-expanding tubular prosthesis isplaced across the neck of the aneurysm in the expanded configuration,the elongated sheath at least partially constraining the radiallyself-expanding tubular prosthesis on the distal segment of the elongatedmetallic wire until the elongated sheath attains the second position.